Two-stage joule-thomson cryostat with gas supply management system, and uses thereof

Abstract

A two-stage Joule-Thomson cryostat (10) has a first-stage cryostat (12) with a helical-coil heat exchanger (14) and and isenthalpic gas expansion orifice (20) that discharges a mixture of cooled gas and cryogenic liquid into a liquid cryogen plenum (26). A second-stage cryostat (30) with a helical coil heat exchanger (32), wound to a larger diameter than the first-stage heat exchanger coil (14), is wound around and in thermal contact with the liquid cryogen plenum (26). This arrangement achieves a high degree of interstage heat transfer and cooling of the gas flowing in the second-stage heat exchanger coil (32) by the liquid cryogen in the first-stage liquid cryogen plenum (26). In operation, a gas flow management system (60), designed for rapid cooldown, initially passes a first gas of high specific refrigerating capacity through both stages (12 and 30). When the stages and structure are sufficiently cooled to the near-vicinity of the normal boiling temperature of the first gas, the flow of the first gas through the second-stage cryostat (30) is discontinued, and flow of a second gas of lower normal boiling temperature than the first gas is passed through the second stage cryostat (30). The flow of the first gas continues through the first-stage cryostate (30).

What is claimed is: 
     
       1. A cooling apparatus, comprising: a first-stage cryostat having   a first-stage heat exchanger coil of tubing, a first-stage Joule-Thomson orifice at a cold end of the first stage heat exchanger coil of tubing, and   a liquid cryogen plenum at the cold end of the heat exchanger coil in which cooled and liquefied gas expanded through the orifice is received; and     a second-stage cryostat having a thermally conducting second-stage support mandrel with an inner dimension greater than the outer dimension of the first-stage heat exchanger coil of tubing and overlying the first-stage heat exchanger coil of tubing,   a second-stage heat exchanger coil of tubing wound upon the second-stage support mandrel, the second-stage heat exchanger coil of tubing extending beyond the liquid cryogen plenum and including a plurality of intercooler turns wound onto, and in thermal communication with, the liquid cryogen plenum, and   a second-stage Joule-Thomson orifice at a cold end of the first-stage heat exchanger coil of tubing.     
     
     
       2. The apparatus of claim 1, wherein the heat exchanger tubing of the first-stage coil is finned. 
     
     
       3. The apparatus of claim 1, wherein the heat exchanger tubing of the second-stage coil is finned, except for the intercooler portion, which is unfinned. 
     
     
       4. The apparatus of claim 1, wherein the first-stage heat exchanger coil of tubing and the second-stage heat exchanger coil of tubing are each wound into a helical pattern. 
     
     
       5. The apparatus of claim 1, further including means for introducing gases into the first-stage cryostat and into the second-stage cryostat.   
     
     
       6. The apparatus of claim 5, wherein the means for introducing includes means for controlling the flow of gases into the first-stage cryostat and into the second-stage cryostat. 
     
     
       7. The apparatus of claim 1, further including a gas flow system controllable to provide a first gas to the first-stage cryostat and the second-stage cryostat under an initial operating condition, and controllable to provide the first gas to the first-stage cryostat and a second gas to the second-stage cryostat under a final operating condition. 
     
     
       8. The apparatus of claim 7, further including a thermal cooling load having a temperature sensor therein. 
     
     
       9. The apparatus of claim 8, wherein the temperature sensor provides a control signal for controlling the flow of gases. 
     
     
       10. A cooling apparatus, comprising: a two-stage cryostat having a first-stage cryostat with a first heat exchanger coil and a first gas expansion orifice, and a second-stage cryostat with a second heat exchanger coil and a second gas expansion orifice; and   a gas supply management system for supplying pressurized gas to the cryostat, the gas supply system including   a first supply source of a first pressurized gas,   a first gas supply line from the first supply source to the first-stage cryostat,   a first gas supply valve in the first gas supply line,   a second supply source of a second pressurized gas,   a second gas supply line from the second supply source to the second-stage cryostat,   a second gas supply valve in the second gas supply line, and   means for controllably permitting the first pressurized gas to flow from the first supply source to the second-stage cryostat when no second gas is flowing from the second gas supply source to the second-stage cryostat, but not permitting the first gas to flow from the first supply source to the second-stage cryostat when the second gas is flowing from the second gas supply source to the second-stage cryostat.   
     
     
       11. The apparatus of claim 10, wherein the means for controllably permitting includes a gas interconnect line from the first gas supply line to the second gas supply line, and   a gas interconnect valve in the gas interconnect line.   
     
     
       12. The apparatus of claim 10, wherein the means for controllably permitting includes a normally open gas interconnect valve between the first gas source and the second-stage cryostat which closes when the second gas supply valve is opened. 
     
     
       13. The apparatus of claim 10, wherein the means for controllably permitting includes a check valve that permits gas to flow from the first gas source to the second-stage cryostat but not in the opposite direction. 
     
     
       14. The apparatus of claim 10, wherein the means for controllably permitting includes a temperature sensor that senses the temperature of a cooling load. 
     
     
       15. The apparatus of claim 10, wherein the means for controllably permitting includes a controller. 
     
     
       16. The apparatus of claim 10, wherein the first gas is selected from the group consisting of argon and Freon-14. 
     
     
       17. The apparatus of claim 10, wherein the second gas is selected from the group consisting of nitrogen and a mixture of nitrogen and neon. 
     
     
       18. The apparatus of claim 10, wherein the two-stage cryostat includes a first-stage cryostat having a first-stage helical heat exchanger coil of tubing,   a first-stage orifice at a cold end of the first stage helical heat exchanger coil of tubing, and   a liquid cryogen plenum at the cold end of the first-stage helical coil in which cooled and liquified gas expanded through the orifice is received; and     a second-stage cryostat having a thermally conducting cylindrical second-stage support mandrel with an inner diameter greater than the outer diameter of the first-stage helical heat exchanger coil of tubing and overlying the first-stage helical heat exchanger coil of tubing,   a second-stage helical heat exchanger coil of tubing wound upon the cylindrical second-stage support mandrel, the second-stage helical coil of tubing extending beyond the liquid cryogen plenum and including a plurality of intercooler turns wound and soldered onto the liquid cryogen plenum, and   a second-stage orifice at a cold end of the first-stage helical heat exchanger coil of tubing.     
     
     
       19. A process for rapidly cooling a thermal cooling load to an operating temperature, comprising the steps of: furnishing a two-stage cryostat having a first-stage cryostat and a second-stage cryostat;   passing a first gas through the first-stage cryostat and the second-stage cryostat to cool the thermal cooling load to an intermediate temperature less than the ambient temperature but greater than the operating temperature;   discontinuing the flow of the first gas through the second-stage cryostat but continuing the flow of the first gas through the first-stage cryostat; and   passing a second gas through the second-stage cryostat, after the flow of the first gas through the second-stage cryostat is discontinued, the first gas having a specific refrigerating capacity greater than the second gas, but the second gas having a normal boiling temperature less than the first gas.   
     
     
       20. The process of claim 19, wherein the first gas is selected from the group consisting of argon and Freon-14. 
     
     
       21. The process of claim 19, wherein the second gas is selected from the group consisting of nitrogen and a mixture of nitrogen and neon. 
     
     
       22. The process of claim 19, wherein the step of discontinuing is performed when the thermal cooling load has been cooled to a preselected temperature. 
     
     
       23. A detector system, comprising: a two-stage cryostat having a first-stage cyrostat with a first heat exchanger coil and a first gas expansion orifice, and a second-stage cryostat with a second heat exchanger coil and a second gas expansion orifice;   a gas supply management system for supplying pressurized gas to the cryostat, the gas supply system including   a first supply source of a first pressurized gas,   a first gas supply line from the first supply source to the first-stage cryostat,   a first gas supply valve in the first gas supply line,   a second supply source of a second pressurized gas,   a second gas supply line from the second supply source to the second-stage cryostat,   a second gas supply valve in the second gas supply line, and   means for controllably permitting the first pressurized gas to flow from the first supply source to the second-stage cryostat when no second gas is flowing from the second gas supply source to the second-stage cryostat, but not permitting the first gas to flow from the first supply source to the second-stage cryostat when the second gas is flowing from the second gas supply source to the second-stage cryostat; and   a sensor in thermal contact with the cryostat.   
     
     
       24. A detector system, comprising: a first-stage cryostat having a first-stage heat exchanger coil of tubing,   a first-stage Joule-Thomson orifice at a cold end of the first stage heat exchanger coil of tubing, and   a liquid cryogen plenum at the cold end of the heat exchanger coil in which cooled and liquefied gas expanded through the orifice is received;     a second-stage cryostat having a thermally conducting cylindrical second-stage support mandrel with an inner dimension greater than the outer dimension of the first-stage heat exchanger coil of tubing and overlying the first-stage heat exchanger coil of tubing,   a second-stage heat exchanger coil of tubing wound upon the second-stage support mandrel, the second-stage heat exchanger coil of tubing extending beyond the liquid cryogen plenum and including a plurality of intercooler turns wound onto, and in thermal communication with, the liquid cryogen plenum, and   a second-stage Joule-Thomson orifice at a cold end of the first-stage heat exchanger coil of tubing; and     a sensor in thermal contact with the second-stage cryostat.   
     
     
       25. A missile having an infrared detector, comprising: a missile having a control system that receives an electrical signal from an infrared sensor;   a two-stage cryostat having a first-stage cryostat with a first heat exchanger coil and a first gas expansion orifice, and a second-stage cryostat with a second heat exchanger coil and a second gas expansion orifice;   a gas supply management system for supplying pressurized gas to the cryostat, the gas supply system including   a first supply source of a first pressurized gas,   a first gas supply line from the first supply source to the first-stage cryostat,   a first gas supply valve in first gas supply line,   a second supply source of a second pressurized gas,   a second gas supply line from the second supply source to the second-stage cryostat,   a second gas supply valve in the second gas supply line, and   means for controllably permitted the first pressurized gas to flow from the first supply source to the second-stage cryostat when no second gas is flowing from the second gas supply source to the second-stage cryostat, but not permitting the first gas to flow from the first supply source to the second-stage cryostat when the second gas is flowing from the second gas supply source to the second-stage cryostat; and   an infrared sensor in thermal contact with the cryostat, the infrared sensor providing an electrical signal to the control system of the missile.   
     
     
       26. A missile having an infrared detector, comprising: a missile having a control system that receives an electrical signal from an infrared sensor;   a first-stage cryostat having a first-stage heat exchanger coil of tubing,   a first-stage Joule-Thomson orifice at a cold end of the first stage heat exchanger coil of tubing, and   a liquid cryogen plenum at the cold end of the heat exchanger coil in which cooled and liquefied gas expanded through the orifice is received;     a second-stage cryostat having a thermally conducting cylindrical second-stage support mandrel with an inner dimension greater than the outer dimension of the first-stage heat exchanger coil of tubing and overlying the first-stage heat exchanger coil of tubing,   a second-stage heat exchanger coil of tubing wound upon the second-stage support mandrel, the second-stage heat exchanger coil of tubing extending beyond the liquid cryogen plenum and including a plurality of intercooler turns wound onto, and in thermal communication with, the liquid cryogen plenum, and   a second-stage Joule-Thomson orifice at a cold end of the first-stage heat exchanger coil of tubing; and   an infrared sensor in thermal contact with the second-stage cryostat, the infrared sensor providing an electrical signal to the control system of the missile.     
     
     
       27. A multiple stage cooling apparatus comprising: a first stage cryostat having a first heat exchanger coil;   a second stage cryostat having a second heat exchanger coil;   means for detecting a specified condition and providing a signal indicative thereof;   a first source of a first gas;   a second source of a second gas; and   means, coupled to said means for detecting and providing and coupled to said first and second sources, for providing gas from said first source to said first and second heat exchanger coils prior to receipt of said signal and, upon receipt of said signal, for stopping supply of said first gas to said second heat exchanger coil and providing said second gas from said second source to said second heat exchanger coil.   
     
     
       28. Apparatus according to claim 27 further including a thermal load and wherein said signal indicates that temperature of said thermal load has dropped below a preselected temperature.